[0001] This invention pertains to milling machines, in general, such as are used to mill
or grind material, the same having interengaging rolls, and in particular to a roll
arrangement, and an inter-roll drive, for a milling machine.
[0002] Known roll milling machines typically incorporate a single, inter-roll drive on one
common end of the opposing rolls. Common designs comprise belt inter-roll drives,
or single gearbox inter-roll drives. Inter-roll drives provide a differential speed
between the opposing rolls of the roll milling machine to enhance grinding. In prior
art machines, one of the opposing rolls is spring-loaded at each end for protection
from tramp metal, rocks, or other foreign material in the feed of the material being
ground. When fine grinding at high horsepowers, the forces of the single, inter-roll
drive at the one common end of the rolls causes an uneven roll nip gap at a given
end of the rolls. The forces of the single-ended, inter-roll drive cause the spring-loaded
roll to move like a lever, with its drive-end bearing serving as the pivot. To date,
no satisfactory solution for this problem has been proposed.
[0003] Further, prior art roll milling machines incorporate a belt-type inter-roll drive
which provides the differential speed between the opposing rolls. A common drive consists
of a drive sheave, a driven sheave, one or more idler sheaves, and a tension mechanism.
A belt or belts gird the sheaves in what is referred to as a serpentine drive. The
prior art tension mechanisms, however, are difficult to disassemble and reassemble,
for the purposes of belt removal and replacement.
[0004] According to the present invention there is provided a roll arrangement for a milling
machine, comprising a frame; a first elongated roll rotatably mounted within the frame,
the first roll having first and second ends and having first sheaves attached at each
end; a second elongated roll rotatably mounted within the frame, the second roll having
first and second ends and having second sheaves attached at each end; and a first
inter-roll drive means coupled to the first and second roll first ends; and characterised
by a second inter-roll drive means coupled to the first and second roll second ends.
[0005] For a better understanding of the invention and to show how the same may be carried
into effect, reference will now be made, by way of example, to the accompanying drawings,
in which:-
FIG. 1 is a plan view of a portion of a milling machine showing a pair of coacting
rollers, according to the prior art;
FIG. 2 is a partial representation of the FIG. 1 illustration, the rollers having
to accommodate a hard, foreign object therebetween;
FIG. 3 is a plan view showing a roll arrangement for a milling machine according to
one embodiment of the invention;
FIG. 4 is an elevational view of the embodiment of FIG. 3;
FIG. 5 is an elevational view of the novel inter-roll drive according to an embodiment
thereof, as is employed at opposite ends of the rolls of FIGS. 3 and 4;
FIG. 6 is an exploded view of the inter-roll drive of FIG. 5; and
FIG. 7 is an elevational view of a preferred embodiment of the inter-roll drive of
the present invention.
[0006] It is desired to provide a roll arrangement for a milling machine which eliminates
the levering of the spring-loaded roll and prevents the excessive gaping between the
coacting rolls. Particularly, it is an object to provide a roll arrangement, for a
milling machine, comprising a frame and a pair of elongated rolls wherein the rolls
have shafts fixed thereto, and rotatably mounted to said frame; and first means supported
by said frame, for biasingly constraining, and yieldably accommodating displacement
of, one of said rolls in rolling engagement with the other thereof; and second means,
coupled to said shafts, for effecting and maintaining a uniform, inter-rolling engaging
force, between said rolls, throughout the full lengths thereof.
[0007] A portion 10 of a milling machine and a pair of coacting rolls 12 and 14 is shown
in FIG. 1. Each roll 12, 14 is journalled in the machine frame 16, and the shafts
thereof are mounted in bearings 18, 20, 22 and 24. At the right-hand end of the rolls
12, 14 (as viewed in FIG. 1) is an inter-roll drive 26, the same represented simply
by dashed-line outlining. Inter-roll drive 26 can be a common belt-type drive. A single,
gearbox, inter-roll drive 28 is mounted to roll 12 and drives both rolls 12, 14. Additionally,
roll 12 is biasingly held against roll 14 by compression springs 30 and 32.
[0008] The inter-roll drive 26 maintains a constant force, between the rolls 12 and 14 at
the right-hand end of the rolls. However, at the opposite ends of the rolls 12 and
14, there is no same force. Consequently, when the rolls must pass tramp metal, rocks,
or other such foreign material, the springs 30 and 32 do not provide for a uniform,
displacement gap.
[0009] FIG. 2 depicts what occurs when a foreign object is introduced between the rolls
12 and 14. Foreign object 34 causes the rolls to compress the springs 30 and 32. However,
because the left-hand end (as viewed in FIG. 2) of the rolls 12, 14 are not constrained
together by a drive mechanism, such as drive 26, the roll 12 is pivoted about the
bearing 22, at its locus 36. While the right hand end of the rolls 12 and 14 are held
to a minimum gaping 38, at the drive end, an unacceptable, excessive gaping 40 occurs
toward the opposite ends of the rolls. Simply, spring 30 yields more than does spring
32.
[0010] FIGS. 3 and 4 depict plan and elevational views of the present roll arrangement 44
which prevents uneven gaping between the rolls, and FIGS. 5 and 6 illustrate the present,
inter-roll drive therefor.
[0011] As shown in FIGS. 3 and 4, the present roll arrangement 44 comprises means coupled
to the shafts of the rolls 12 and 14, and 12a (shown in FIG. 5) and 14a, for effecting
and maintaining a uniform, inter-rolling engaging force, between the rolls, throughout
the full lengths of the rolls. At each end of the rolls 12, 14, 12a and 14a are inter-roll
drives 46, of the belt-type in this embodiment. The rolls 12 and 12a are still biasingly
held against the coacting rolls 14 and 14a, by springs 30 and 32 (and 30a and 32a),
but the driving engagement of the roll shafts, at the opposite ends of the rolls prevents
rolls 12 and 12a from pivoting about the bearings 22 and 22a. Whatever foreign material
will be encountered by the rolls 12, 12a, 14 and 14a, the rolls 12 and 12a will displace
from the rolls 14 and 14a to define a uniform gap along the length of the rolls. The
dual-ended, inter-roll drives 46 maintain the uniform, inter-rolling engaging force
between the rolls.
[0012] The inter-roll drive(s) 46, shown in FIGS. 5 and 6, comprises the usual serpentine
arrangement of belting about sheaves. However, the same comprises means for facilitating
removal and replacement of the belting, when necessary, without requiring complete
disassembly of the drive for the purpose. In lieu of the belt drives 46 shown in FIGS.
3 to 7, two gearbox inter-roll drives can be used. Gearbox drives are typically used
when higher horsepower is needed.
[0013] Inter-roll drive 46 comprises a pair of generally right-angularly formed brackets
48 and 50. A pair of idler sheaves 52 and 54 are journalled on shafts 56 and 58. The
latter are held in the brackets 48 and 50 in bushings 60. Spacers 62 and their associated
hardware are interposed between the brackets 48 and 50 to support the brackets and
hold them apart. The roll sheaves 64 and 66, the former 64 being smaller in diameter
than the latter 66, are coupled to their respective roll shafts 68 and 70. Idler shaft
58 is greater in length than shaft 56, as its inner end is journalled in an aperture
72 provided in the frame 16. Belting 74 wraps or girds the sheaves 52, 54, 64, and
66. Leading ends of the brackets 48 and 50 have slots 76 formed therein; the slots
76 receive therein the annularly grooved ends of a rod or pivot pin 78.
[0014] Sheaves 64 and 66 are relatively stable in positioning, for being mounted to the
roll shafts therefor. However, because idler shaft 58 is journalled in the aperture
72, a counter-clockwise rotation of the brackets 48 and 50, with their mounted components,
will tighten the belting 74. Conversely, if the brackets 48 and 50, and mounted components,
are rotated in a clockwise direction, the belting will become slack and readily removable
from the sheaves 52, 54, 64 and 66 for replacement.
[0015] The present drive 46 includes means for tensioning the brackets 48 and 50 and biasingly
holding them in a relatively counter-clockwise disposition, to keep the belting 74
tight. The same tensioning means also accommodates release of the tensioning, and
rotation of the brackets 48 and 50 in the clockwise direction, to facilitate an effortless
replacement of the belting 74, without requiring a major disassembly of the drive
46.
[0016] The frame 16 has, in a lower portion thereof, an aperture 80. Aperture 80 receives
the dowel end of a first bar 82 rotatably therein. The bar 82 has a pair of boreholes
84 formed therein. Boreholes 84 slidably receive a pair of rods 86 which extend from
a second bar 88. In addition, first bar 82 has a tapped hole 90 formed therein, and
second bar 88 has an untapped hole 92 formed therein. A bolt 94 threaded through bar
82 and bar 88 via the hole 92 bears against the pivot pin or rod 78. Finally, compression
springs 96 on rods 86, and between the bars 82 and 88 maintain an optimum pressure
between the bars 82, 88. This tensioning means maintains the brackets 48 and 50 in
a relatively counter-clockwise, belting-tightened position. However, by loosening
the bolt 94, and allowing the tensioning arrangement to rotate in the clockwise direction,
the belting 74 becomes loose on the sheaves and is easily removed and replaced. A
nut 98 is provided on the bolt 94 for tightening the bolt in the desired tensioning
position. Also, a scale holder 100 and its associated graduated scale 102, are mounted
onto the second bar 88. These items offer a means of repositioning the tensioning
arrangement.
[0017] Upon loosening bolt 94, the pressure on the rod or pivot 78 is relieved and, accordingly,
it can then be extracted from the slots 76 in the brackets 48 and 50. With the tension
relieved, the bars 82 and 88, and the incorporated springs 96, can be rotated on the
journalled dowel-end of bar 82 and swung up out of the way, giving access to the rod
or pivot pin 78.
[0018] FIG. 7 shows a preferred embodiment of the belt inter-roll drive. A third idler sheave
53 is included to allow the belting 74 to wrap more then 180 degrees around the roll
sheave 66. This causes the belt inter-roll drive to transmit more power to sheave
66.
1. A roll arrangement (44) for a milling machine, comprising a frame; a first elongated
roll (12) rotatably mounted within the frame, the first roll (12) having first and
second ends and having first sheaves (66) attached at each end; a second elongated
roll (14) rotatably mounted within the frame, the second roll having first and second
ends and having second sheaves (64) attached at each end; and a first inter-roll drive
means (46) coupled to the first and second roll first ends; and characterised by a
second inter-roll drive means (46) coupled to the first and second roll second ends.
2. A roll arrangement according to claim 1, further comprising a main drive means, operably
connected to the first inter-roll drive means (46), for providing drive power to the
first inter-roll drive means (46), power being provided through the first roll (12)
to the second inter-roll drive means (46).
3. A roll arrangement according to claim 1 or 2, wherein the first and second inter-roll
drive means (46) are belted drive means.
4. A roll arrangement according to claim 3, wherein the first and second inter-roll belted
drive means (46) each include a plurality of idler sheaves (52, 54) rotatable mounted
within the frame and a drive belt (74), the first and second sheaves (66, 64) and
the idler sheaves (74) being configured such that the first roll rotates in an opposite
direction to the second roll (14) and each drive belt engages more than half the circumference
of the first sheave (66) and the second sheave (64).
5. A roll arrangement according to claim 4, wherein the number of idler sheaves (52,
53, 54) for each drive means is three and each belt (74) passes around the three idler
sheaves, then the first sheave (66), then the second sheave (64).
6. A roll arrangement according to any one of the preceding claims, wherein the diameter
of the first sheave (66) is greater than the diameter of the second sheave (64).
7. A roll arrangement according to claim 3, or claim 4, 5 or 6 as appendant to claim
3, wherein the first and second belted drive means each include a drive belt (74),
each drive belt engaging more than half the circumference of the first sheave (66)
and the second sheave (64).
8. A roll arrangement according to claim 1 or 2, wherein the first and second inter-roll
drive means are gear drive means (46).
9. A roll arrangement according to any one of the preceding claims, further comprising
a means for biasing the first roll towards the second roll.